Lordosis in the male golden hamster elicited by manual stimulation: characteristics and hormonal sensitivity

The lordosis response was regularly elicited from 24 of 31 intact, adult male hamsters, using manual somatosensory stimulation of the dorsal rear body. In these males there was no correlation between measures of male-typical behavior and lordosis. Castration had no effect on male lordosis duration scores even when intromissions were eliminated. Combined treatment with estradiol benzoate and progesterone significantly increased male lordosis duration scores. The body surface was mapped with a standardized brush stimulus. For eliciting lordosis, effectiveness of stimulation increased in an almost identical manner for hormone-primed males and females from the anterior to the posterior part of the body, with the stimulation of flanks, rump, and perineum the most effective. Within each skin zone, absolute effectiveness was greater in females than in males. Various types of somato-sensory stimulation were compared for their effectiveness in eliciting lordosis. Females were more responsive to these stimuli than males, even when males were hormonally primed. These behavioral data have implications for concepts of the neural organization of male- and female-typical mating responses existing within the same individual.     

Prelordotic behavior in the hamster: A hormonally modulated transition from aggression to sexual receptivity.

Analyzed the behavioral responses of 60 female golden hamsters to sexually experienced males as a function of the stage of the female's estrous cycle. Exogenous estradiol or estradiol followed by progesterone was given to ovariectomized Ss to determine the role of these hormones in regulation of cyclic changes in the female's response to the male. Ss were paired daily with sexually active males for 10 min, and behavioral interactions were recorded. Significantly more fighting occurred during early diestrus than later in the cycle. By 8 hrs prior to the onset of sexual receptivity, 86% of Ss exhibited a behavior resembling the onset of lordosis without immobilization. Following ovariectomy, fighting was at a high level. Estradiol replacement over 28 days resulted in a significant decrease in aggression and increase in display of the prelordotic response. Initially, treatment with progesterone following 7 days of estradiol caused lordosis display. After 24 hrs a significant increase in aggression, which continued as long as progesterone was present, was observed. Thus, estradiol causes the female to become tolerant of the male's approach, the female exhibiting prelordosis in response to the male's investigation. Estradiol and progesterone are necessary for normal sexual receptivity; however, after 24 hrs, estrogen/progesterone-treated females become agonistic to the male. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mating-induced inhibition of receptivity in the female golden hamster (Mesocricetus auratus): II. Stimuli mediating short-term effects.

In the female golden hamster, mating with an intact male results in reduced receptivity toward a second male. In Experiment 1, females received various types of mating stimuli (e.g., mounts from an aproned male, intromissions from a vasectomized male, a simulated copulatory plug, a male in a hardware cloth cylinder, or several of these stimuli in combination). Although stimuli associated with male intromissions appeared to be most effective in altering the female's responsiveness to a subsequent male, treatments that included intromissive stimuli also resulted in the longest periods of lordosis. In Experiment 2 we found a highly significant inverse relation between the duration of lordosis in the presence of a male enclosed in a hardware cloth cylinder and lordosis duration with a second male that was free to copulate. In Experiment 3 we further showed that it was not the presence of a male in the cylinder that was the essential stimulus for producing this effect but rather the act of lordosis itself. By varying lordosis time and the number of intromissions independently (Experiment 4), we convincingly showed that short-term inhibition of receptivity in the hamster is attributable to lordosis duration per se rather than to male intromissions, as had been previously reported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habenular lesions and feminine sexual behavior of ovariectomized rats: Diminished responsiveness to the synergistic effects of estrogen and progesterone.

Bilateral electrolytic lesions in the habenula resulted in disruption of feminine sexual behaviors evoked by estrogen and progesterone in 43 ovariectomized rats. There were no differences between lesioned and sham-operated Ss in tests conducted after the administration of estrogen alone. Ss with lesions were characterized by an increased proportion of mounts not followed by lordosis, a decreased proportion of mounts followed by pronounced lordosis, and a decreased proportion of mounts preceded by soliciting behaviors. Lesions had a negligible effect upon the tendency to hold lordotic postures after the male dismounted. Results suggest that the habenula is involved in modulating responsiveness to the synergistic effects of estrogen and progesterone. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of gonadal hormones and sexual behavior on ultrasonic vocalization in rats: I. Treatment of females.

Ultrasonic vocalizations were measured when male Long-Evans rats were placed with ovariectomized females that had experienced various hormonal and behavioral treatment. In Exp I, 18 males were tested with females in each of the following conditions: nonestrous (OVX), estrogen treated (E), estrogen and progesterone treated (EP), and estrogen and progesterone treated and given 2 intromissions from a stud male prior to testing (EPI). Control conditions included clean cage (CL) and cage soiled by an estrous female (SOI). The treatments differed in effect on rate and maintenance of vocalization, in the order of greatest to least: EP, E, EPI, and OVX (equal), SOI, and CL. In tests in which males produced a high rate of vocalization, some males with short intromission latencies shifted from the normal 50-kHz pulse to a 22-kHz pulse. In Exp II, the effect of the female's vocalization and movement on the rate of and latency to vocalization was measured. 21 males were presented with each of the following stimulus conditions: estrous female with red light (EP), estrous female without red light (EP dark), estrous anesthetized female (EP anes), and nonestrous anesthetized female (OVX anes). Effects on vocalization of various treatments were in descending order: EP and EP-dark (equal), EP anes, and OVX anes. Data suggest that the 50-kHz vocalizations constitute a graded response influenced by the female's hormonal and sexual condition. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of a muscarinic antagonist on various components of female sexual behavior in the rat.

Effects of the muscarinic antagonist scopolamine on lordosis, solicitation, pacing, approach, attractivity, and activity were evaluated in ovariectomized rats brought into sexual receptivity with estrogen and progesterone. Systemic (1 mg/rat) or intraventricular (10 μg bilaterally) administration of scopolamine significantly reduced the incidence of lordosis and solicitation behaviors and disrupted typical pacing of sexual contacts with a stimulus male. In addition, females avoided contact with a stimulus male, but not a stimulus female, following intraventricular infusion of scopolamine. The levels of general activity and frequencies of sexual contacts were similar in females treated intraventricularly with scopolamine and vehicle solutions. Consequently, scopolamine disrupted various components of sexual behavior, including lordosis, solicitation, pacing, and approach, without altering female attractivity or general activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypophysectomy facilitates sexual behavior in female rats

Lordosis was elecited in 49% of 87 hormonally untreated, hypophysectomized-ovariectomized (hypox-ovx) female rats in response to palpation of the flanks and perineum (vaginal stimulation was not applied). By contrast, only 12% of 113 hormonally untreated ovariectomized (ovx) rats showed lordosis in response to such stimulation. Subsequently, hypox-ovx and ovx-only rats were given daily injections of 1 mug/kg estradiol benzoate (EB) and tested for sexual receptivity with males. Teh estrogen-treated hypox-ovx females became sexually receptive significantly earlier, and exhibited higher lordosis quotients and more soliciting behavior, than the estrogen-treated ovx-only rats. The increased sexual responsiveness in the hypox-ovx rats could be due to increased LRH activity. To test this, we treated hypox-ovx rats with dihydrotestosterone propionate (DHT-P), which suppresses plasma LH levels but is relatively ineffective in inducing sexual receptivity, and found a significant depression of lordosis responsiveness. These experiments suggest that hypox-ovx females show a heightened responsiveness to hormonal and/or sensory factors that induce a lordosis response, possibly because of increased LRH activity.     

Effects of sex hormones on protein and collagen content of the temporomandibular joint disc of the rat

PURPOSE: The effect of sex hormones on the protein and collagen content of the temporomandibular joint (TMJ) disc of adult male and female rats. MATERIALS AND METHODS: One hundred forty-four Wistar rats were assigned to 14 groups of 12 each. Two groups, one female and one male, served as a control and received no treatment, and two other groups (one female and one male) received a sham gonadectomy and placebo hormone. The remaining 10 groups (five males and five females) received either orchiectomy or ovariectomy, followed by administration of estrogen, progesterone, combined estrogen and progesterone, or testosterone. The total protein and collagen content of the TMJ disc were determined using the calorimetric hydroxyproline method. RESULTS: The collagen content of TMJ discs of control males was statistically greater than the collagen content of the control female rats. This difference disappeared after ovariectomy of females and orchiectomy of males. Also, there was a general trend for a decrease in collagen and protein content to be produced by estrogen, progesterone, and by estrogen combined with progesterone in castrated male and female rats, and by orchiectomy of male rats. There was also a trend toward an increase in collagen and protein content after ovariectomy in female rats and administration of testosterone to castrated male and female rats. However, the only statistically significant effect of the drugs tested was that of estrogen combined with progesterone in ovariectomized female rats (a lowering effect on the total protein) and of estrogen alone in orchiectomized male rats (a lowering effect on the collagen content). CONCLUSION: Steroid sex hormones have an effect on the collagen and protein content of the TMJ disc of the rat as indicated by the difference in the values between control males and females and by the disappearance of this difference on castration of both male and female animals. This was also manifested by the significant effect of estradiol on collagen content of castrated males, by the effect of estrogen combined with progesterone on the protein content of castrated females.     

Central progesterone induces female sexual behavior in estrogen-primed intact male rats.

Injection of progesterone induced high levels of female lordotic behavior in 10 of 47 intact, estrogen-primed male Sprague-Dawley rats when it was applied directly to the medial preoptic/anterior hypothalamic area. All 17 Ss previously had shown lordosis when the serotonergic antagonist methysergide was applied to the same central sites. Few Ss responded to systematic progesterone and none to intracranial cholesterol. Intradiencephalic Metycaine, a local anesthetic, induced lordosis in 8 Ss that previously had responded to central progesterone. These data indicate that estrogen and progesterone act synergistically to induce lordosis in male rats when progesterone is administered directly to sensitive brain sites. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assuring quality, information, and choice in managed care

The aim of the study was to determine whether there is an increase in responsiveness to estrogen stimulation of maternal behavior and lordosis responsiveness during pregnancy. Using separate groups of pregnancy-terminated females, we measured the initial maternal responsiveness of hysterectomized-ovariectomized (HO) females and their responsiveness to estrogen stimulation. Maternal behavior latencies were studied in females HO on the 8th, 10th, 13th, 16th, or 19th day of pregnancy (8HO-19HO) and in nonpregnant HO (NPHO) females. Groups were injected sc with estradiol benzoate (EB) in doses ranging from 0 to 200 microgram(s)/kg and tested for maternal behavior (retrieving, crouching, and licking pups). In addition, we investigated whether there is an increase during pregnancy (following HO) in lordosis responsiveness to estrogen stimulation. Lordosis behavior was studied in pregnant HO females (days 8, 16, and 22) and NPHO females given 0 to 200 microgram(s)/kg EB. There was an increase in maternal responsiveness in oil-treated HO females starting around midpregnancy. From early pregnancy on there was also an increase in maternal responsiveness to 20 microgram(s)/kg EB. In late pregnant females (16HO) there was a further increase with 50 microgram(s)/kg EB. There was no increase in lordosis responsiveness to EB stimulation during pregnancy; pregnant and nonpregnant HO females had the same EB threshold for stimulating lordosis behavior. The results of both studies were related to increases during the latter half of pregnancy in nuclear estrogen receptor concentrations in the MPOA, an area that mediates estrogen stimulation of maternal behavior, and the absence of such increases during pregnancy in the VMH, an area that mediates estrogen stimulation of lordosis behavior.     

Cholinergic influences on estrogen-dependent sexual behavior in female rats.

Examined the ability of cholinergic agents to influence hormone-dependent sexual behavior in Sherman rats. In Exp I, sexual behavior, indicated by the incidence of lordosis, was significantly increased in estrogen-treated Ss following bilateral infusion of a cholinergic receptor agonist, carbachol (.5 μg/cannula) into the medial preoptic area of the brain. Infusion of an artificial cerebrospinal fluid vehicle failed to facilitate lordosis. The incidence of lordosis was normally highest 15 min after carbachol infusion began to wane by 45 min, and had returned to control levels by 90 min. Centrally administered carbachol activated lordosis at lower levels of estrogen priming than did systemically administered progesterone. In Exp II, Ss brought into sexual receptivity by administration of estrogen and progesterone received preoptic infusions of an acetylcholine synthesis inhibitor, hemicholinium-3 (HC-3). Significant reductions in the incidence of lordosis were observed following bilateral infusion of HC-3 (1.25 μg/cannula). This inhibition of lordosis was prevented when carbachol (.5 μg/cannula) was infused along with HC-3. Results confirm the importance of cholinergic influences on sexual behavior in female rats. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female lordotic behavior mediated by monoamines in male rat.

In Exp I direct application of serotonergic or b-adrenergic receptor blockers to anterior or posterior areas of the hypothalamus induced lordosis in 18 intact estrogen-primed male Sprague-Dawley rats. Such treatment with an a-adrenergic blocker or systemic administration of progesterone failed to increase lordosis. In Exp II (n = 7) centrally elicited lordosis did not occur without estrogen priming. It is concluded that anatomical and neurochemical similarity may exist in the brain mechanism mediating lordotic behavior in male and female adult rats. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrogen-progesterone regulation of nest-building and incubation behavior in ovariectomized ring doves (Streptopelia risoria).

Determined the role of ovarian hormones in the induction of nest-building (tucking) and incubation behavior in female doves by systemic injections of estrogen, or progesterone, or estrogen combined with progesterone, or oil in 40 reproductively experienced, ovariectomized Ss. Combined estrogen and progesterone treatment was the most effective hormone regimen for eliciting both behavior patterns in females and also facilitated these behaviors in their 40 untreated mates. Differences in role of the gonadal progesterone in male and female doves are discussed. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aggressive behavior in female hamsters: The hormonal basis for fluctuations in female aggressiveness correlated with estrous state.

The frequency and sequencing of aggressive behaviors by naive female hamsters has been found to change during series of brief encounters, probably because of the lack of stable dominance relations. Such initial encounters seem most representative of interactions likely in free-ranging hamsters and have been emphasized in studies of the hormonal mediation of female aggression. The present 4 experiments, conducted with a total of 72 random-bred female hamsters, found that nonestrous females exhibited intense aggression toward conspecifics of either sex. Estrous females were not aggressive and spent much time in lordosis, indicative of sexual receptivity. While oil-injected adrenalectomized-ovariectomized females fought at high levels, comparable with intact nonestrous females, the combination of 17-β-estradiol benzoate and progesterone suppressed fighting completely. In contrast, replacement of estradiol, progesterone, or testosterone propionate individually had no consistent effect. Hypophysectomized females also fought at high levels, indicating that pituitary hormones are not required for vigorous aggression. Further, individual anterior pituitary hormones did not produce marked changes in fighting. Results emphasize the roles of estrogen and progesterone in synchronizing aggression with current reproductive state. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of CNS depressants and stimulants on latency for the appearance of copulatory response in the female rat

Diethyl ether anesthesia, sodium hexobarbital (20 mg/kg), diphenylhydantoin (50 mg/kg), strychnine (1 mg/kg) and picrotoxin (1-0.25 mg/kg) effectively induced the copulatory response (lordotic behavior) in estradiol benzoate treated ovariectomized rats although no progesterone was given. As none of the tested compounds were effective in replacing progesterone in adrenalectomized animals, adrenal secretion is likely to be implicated in the lordosis activating effect of these compounds. The lordosis response appeared faster after the CNS stimulants than after treatment with the CNS depressants. The influence of diethylether anesthesia, strychnine (0.5 mg/kg) or picrotoxin (0.25 mg/kg) on the latency for the appearance of the lordosis response after IV injection of isopregnenone was studied in estradiol benzoate treated ovariectomized females. A 10 min ether anesthesia delayed the onset of the lordosis response in adrenal intact as well as adrenalectomized animals. Anesthesia given after receptivity had been fully established suppressed the responses for a short period (10-30 min) after the narcosis. The delay of the appearance of the first lordosis response after IV injection of isopregnone exceeded this period. Strychnine but not picrotoxin significantly shortened the latency to the onset of the female copulatory response. It is concluded that the lordotic activating action of progesterone or steroids with progesteronelike ability released from an endogenous source or given IV is influenced by compounds which exert a depressant or stimulant effect on neuronal activity. The total response obtained is not changed but the appearance of the response is prolonged by CNS depressants and shortened by certain CNS stimulants.     

Estradiol benzoate facilitates lordosis and ear wiggling of 4- to 6-day-old rats.

The effects of exogenous and endogenous steroids on components of female sexual behavior of neonatal male and female rats were investigated. In Experiment 1, 4-day-old rats were treated with 0, 0.1, 1.0, 10, or 100 μg/10 g body weight estradiol benzoate (EB) and were tested 44 hr later. In Experiment 2, male rats castrated within 24 to 48 hr of birth were compared with sham operated controls and castrates given steroid replacement. The results indicated that most 6-day-old pups will display lordosis and ear wiggling, therefore, the display of these responses is not dependent upon exogenous steroids. However, a fine-grain behavioral analysis revealed that EB treatment increased the frequency, duration, and intensity of lordosis and the frequency of ear wiggling in infant females, and it increased lordosis duration in males. Castration of infant males decreased the likelihood that male infants would display lordosis, whereas testosterone replacement restored behavior to control levels. These data question the concept that organizational and activational actions of estrogens occur during completely separable times in development and should provide new insights into the development of estrogen receptor function and the process of sexual differentiation of brain and behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motion picture analysis of rat mating behavior.

Studied the interaction and coordination of male and female rats during mounting and lordosis, using 12 primiparous female and 4 male Sprague-Dawley rats. Head, body, and limb movements of the female are described in relation to forelimb and pelvic movements of the male during mounting. Data show that (a) mounts with ejaculation were longer than mounts without ejaculation; (b) during mounts with ejaculation or intromission, the elevation of the female's head was maintained after perineal contact was lost; whereas when there was no deep vaginal penetration, the head began lowering before loss of perineal contact; and (c) lordosis persisted longest after dismount when intromission accompanied mounts. The following objective definition of lordosis is provided: Onset is the beginning of head elevation; termination is the raising of a paw from the floor of the cage after dorsiflexion of the vertebral column. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Localization in the amygdala of the amnestic action of diazepam on emotional memory

Electrical lesions of the medial preoptic area/anterior hypothalamus (MPOA/AH) have been reported to enhance the display of steroid-induced lordosis in castrated male rats. This study employed the cell body-specific neurotoxin, ibotenic acid, to ascertain whether neurons originating in this region (as opposed to axons of passage) tonically inhibit steroid-induced lordosis in adult male rats. Castrated, adult Long-Evans males received bilateral electrical lesions or injections of ibotenic acid or vehicle aimed at the MPOA/AH. Following administration of estradiol benzoate (EB) and progesterone, lordosis quotients (LQs) and lordosis ratings (LRs) were significantly higher in groups of rats with electrical lesions (LQ = 62.2 +/- 15.1; LR = 1.22 +/- 0.34) and ibotenic acid-induced lesions (LQ = 58.1 +/- 12.2; LR = 0.99 +/- 0.24) than in the control group (LQ = 12.8 +/- 7.3; LR = 0.22 +/- 0.13). To determine whether this enhancement of receptive behavior in MPOA/AH-lesioned males was an effect on estradiol-induced, as compared to progesterone-facilitated lordosis, groups of castrated rats in a second experiment received bilateral injections of ibotenic acid or vehicle aimed at the MPOA/AH and were tested for lordosis after administration of EB alone and again after injection of progesterone. Following treatment with EB alone, rats with ibotenic acid-induced MPOA/AH lesions tended to be slightly less receptive than control animals. However, following injections of progesterone, LQs and LRs were higher in the MPOA/AH-lesioned group than in the control animals, as had been observed in the first experiment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Urine marking and maternal aggression of wild female mice in relation to anogenital distance at birth

A series of experiments were conducted with wild house mice to verify the effect of intrauterine position on females' anogenital distance at birth (AGD) and to examine the relationships between a female's AGD, used as a bioassay of androgen exposure during fetal life, and her social behavior and reproductive success in adulthood. Experiment 1 showed that cesarean-delivered females that developed in utero between two males (2 M females) have significantly longer AGD's than females positioned between two females (0 M females). We then categorized naturally delivered females shortly after birth as having a long, medium or short AGD. In adulthood, these females were tested for their behavior towards unfamiliar pups, their rate of urine-marking in response to a variety of social stimuli, postpartum aggression and success in protecting their litters in response to male and female intruders. Adult females with different AGD's at birth did not differ either in their behavior toward pups or in their rate of urine marking. Conversely, males housed across a wire mesh partition from a long-AGD female deposited a higher number of urine marks than those exposed to a short-AGD female. When tested after delivering a litter, long-AGD females displayed more tail-rattling (a component of agonistic behavior) towards intruders of both sexes in comparison to short-AGD females. These results are consistent with the hypothesis that females with a long AGD are exposed to higher levels of Testosterone during fetal life than females with a short AGD. Although not related to AGD, other measures of maternal aggression were affected by postpartum day, sex of intruders and a female's infanticidal potential while a virgin.     

"Estrogen-Progesterone Regulation of Nest-Building and Incubation Behavior in Ovariectomized Ring Doves (Streptopelia risoria)": Erratum.

Reports an error in the original article by Mei-Fang Cheng and Rae Silver (Journal of Comparative & Physiological Psychology, 1975[Jan], Vol 88[1], 256-263). The address for the request for reprints should have read "Institute of Animal Behavior, Rutgers University, Newark, New Jersey 07102." (The following abstract of this article originally appeared in record 1975-08949-001.) Determined the role of ovarian hormones in the induction of nest-building (tucking) and incubation behavior in female doves by systemic injections of estrogen, or progesterone, or estrogen combined with progesterone, or oil in 40 reproductively experienced, ovariectomized Ss. Combined estrogen and progesterone treatment was the most effective hormone regimen for eliciting both behavior patterns in females and also facilitated these behaviors in their 40 untreated mates. Differences in role of the gonadal progesterone in male and female doves are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)